This tumor-suppressive role has been suggested to be due to different pathways, including matrix metallopeptidase 9 (MMP-9) and matrix metallopeptidase 13 (MMP-13) down-regulation in lung mucoepidermoid carcinoma [70], as well as VEGF and MMP-9 downregulation in pancreatic and prostate cancers [73,74,75]. Here, MMP13 is linked to pulmonary mucoepidermoid carcinoma.